This invention pertains generally to the field of integrated optical components for use in fiber optic communications systems, and more particularly it relates to photonic switching. Specifically the invention is a 1 .times.2 integrated optical switch having a very high extinction ratio.
Since metal diffused LiNbO.sub.3 waveguides were first fabricated in 1974, LiNbO.sub.3 -based integrated optical devices, such as modulators and switches, have been extensively studied and the results of such studies have been reported in the literature. This interest in such devices has been based on the expectation that integrated optical devices will play an important role in optical communications systems, especially in optical switching. In optical time-division switching, integrated optical switches are the key elements of optical shift registers and optical time-slot interchangers. In optical space-division switching, integrated optical modulators and switches are the major elements at the crosspoints for all types of switching architectures.
The most important characteristic that an integrated optical switch must have for space-division switching applications is a high extinction ratio. The presently available, conventional 1 .times.2 integrated optical switches have extinction ratios ranging from 15 dB to 25 dB. These low extinction ratios of the presently available integrated optical switches effectively prevents such switches from being integrated into large switch matrices, which matrices are very desirable for optical broadband switching.